If you were to boot either in auto form, the performance would be virtually identical, just one would see a few more revs.

....

However we break up the increments, in-gears, etc., through the gears there's nothing in it, when both are stretched.

Yeah absolutely. But you understand you're agreeing with what I said innit

Quote:

Originally Posted by MaestroAl

0-60 is the least interesting time. 20-40, 40-60, 40-100, 60-90, 50-70 ... these are all real times and the 330D would ... leave the 328i for dead ... at any of those measures in any gear As I said before, other than on full reheat at 5000rpm+, the 330D would beat the 335i at any of those measures BHP is all talk but torque is fo' real

OK, so we are in a manual 330d and a manual 335i, we hold our gear and accelerate, then torque clearly does shows its edge. That is assuming our revs are near equal and the gear/gearing is the same.

Now swap to our auto versions and we come up behind a car to overtake, we want the fastest performance... we flick to sport and floor it... 50 - 70mph is near identical, we just see a different rev limit. Performance is near identical. High torque is not giving any acceleration advantage, as we now are in the real mix of rpm, torque and hp. Which ever engine we have feels good and does the job just as effectively.

The 330d and 328i are very closely matched in performance. Although the 328i is more nimble and therefore quicker in the twists. 50 - 90 mph, typical motorway joining speeds both are in the 7 second bracket.

You certainly have to work a bit harder for the performance in the 328i. I have an colleague with the F30 330d and rolling on from 60 to whatever speed you like there was little in it. The big difference was all he had to do to access the performance was stamp on the throttle, whilst I needed to be in the right gear. If youre lazy in the 328i then you will get left by the 330d.

You're kinda missing the point with this whole Torque Vs Power argument.

Soooo.... a couple of facts from the world of physics to help straighten things out Power (bhp/kW) is only a factor when it comes to ultimate, out-and-out top speed. That is all. End of. It has literally NO bearing on acceleration. None. Zip. Nada. Torque is the ability of the engine to turn the wheels and accelerate the car. Power is there to overcome overall friction - in this case in the form of tyre, air and mechanical friction.

Now you understand that, you'll understand why torque is all that matters in the real world. The reason that an M3 will accelerate faster than a 330D or any other high torque/low rpm car for that matter, is the way in which it delivers its power. The critical factor in this is the gearbox. A gearbox ... get this ... is a torque multiplier. That's all it is. Simples.

So take a 330D at 3000rpm giving out 400 ftlbs of torque (I'm making these numbers up for the sake of our little experiment here) and then take an M3 [i]at the same speed but in a different gear ratio so that it's at 6000 rpm and giving out 300ftlbs of torque. Since the M3 is at twice the engine speed of the 330D here, it is running twice the gear ratio and so its torque, relative to the 330D, is doubled. I'm not saying it's putting out 600ftlbs here, just that the final torque to the drivetrain will be double that of the 330D at the same speed in this instance. that's why an F1 car with a tiny 2.4l V8, putting out a miserly 200ftlbs of torque can move like the clappers. That 200ftlbs of torque is developed from 17k to 18k rpm so you get huge multiplication from the gearbox. Same goes for bikes.

However, and here's the killer, who drives like that on a normal day? Nobody for long anyway To get that "fast feeling" (which is simply forward acceleration for most people), one simply needs to put one's foot down in any gear at any speed in a car with tonnes of torque and you're off. A normal overtake from 60-80mph in top gear ... the 30D will hand the M3's ass back to it Most driving, done between 1500 and 4000 rpm is right in the 30D's sweet spot where maximum torque is available whereas the M3 isn't even on cam by then. Same goes for the 335i. And I know I've said this a million times (especially over in the American forum 'cause it's soooo rewarding) but the 335i and, to a lesser extent the M3, is only quicker than the 30D when you wind the nuts off it. Under all other circumstances, it's slower.

So next time you look at a car's performance figures, look a little closer and see the bigger picture. I honestly have no idea why the automotive world still goes on about bhp in 90% of cars. it only matters in hypercars where going over 200mph is an issue. What's your maximum torque and at what rpm is it developed. Only then can you compare like for like in the real world. And forget Top Gear lap times, they're only of use for entertainment (which they surely are) and are the TV equivalent of a bedroom poster. Torquey cars just feel quicker for 90% of driving. It's only a matter of physics and it's all about torque.

You're kinda missing the point with this whole Torque Vs Power argument.

Soooo.... a couple of facts from the world of physics to help straighten things out Power (bhp/kW) is only a factor when it comes to ultimate, out-and-out top speed. That is all. End of. It has literally NO bearing on acceleration. None. Zip. Nada. Torque is the ability of the engine to turn the wheels and accelerate the car. Power is there to overcome overall friction - in this case in the form of tyre, air and mechanical friction.

Now you understand that, you'll understand why torque is all that matters in the real world. The reason that an M3 will accelerate faster than a 330D or any other high torque/low rpm car for that matter, is the way in which it delivers its power. The critical factor in this is the gearbox. A gearbox ... get this ... is a torque multiplier. That's all it is. Simples.

So take a 330D at 3000rpm giving out 400 ftlbs of torque (I'm making these numbers up for the sake of our little experiment here) and then take an M3 [i]at the same speed but in a different gear ratio so that it's at 6000 rpm and giving out 300ftlbs of torque. Since the M3 is at twice the engine speed of the 330D here, it is running twice the gear ratio and so its torque, relative to the 330D, is doubled. I'm not saying it's putting out 600ftlbs here, just that the final torque to the drivetrain will be double that of the 330D at the same speed in this instance. that's why an F1 car with a tiny 2.4l V8, putting out a miserly 200ftlbs of torque can move like the clappers. That 200ftlbs of torque is developed from 17k to 18k rpm so you get huge multiplication from the gearbox. Same goes for bikes.

However, and here's the killer, who drives like that on a normal day? Nobody for long anyway To get that "fast feeling" (which is simply forward acceleration for most people), one simply needs to put one's foot down in any gear at any speed in a car with tonnes of torque and you're off. A normal overtake from 60-80mph in top gear ... the 30D will hand the M3's ass back to it Most driving, done between 1500 and 4000 rpm is right in the 30D's sweet spot where maximum torque is available whereas the M3 isn't even on cam by then. Same goes for the 335i. And I know I've said this a million times (especially over in the American forum 'cause it's soooo rewarding) but the 335i and, to a lesser extent the M3, is only quicker than the 30D when you wind the nuts off it. Under all other circumstances, it's slower.

So next time you look at a car's performance figures, look a little closer and see the bigger picture. I honestly have no idea why the automotive world still goes on about bhp in 90% of cars. it only matters in hypercars where going over 200mph is an issue. What's your maximum torque and at what rpm is it developed. Only then can you compare like for like in the real world. And forget Top Gear lap times, they're only of use for entertainment (which they surely are) and are the TV equivalent of a bedroom poster. Torquey cars just feel quicker for 90% of driving. It's only a matter of physics and it's all about torque.

Simples

Nice write up ......but wrong Power is the real engine performance indicator

Yep, I'm with Maestro and Isaac Newton on this.
For any given vehichle speed max acceleration occurs at peak power. But in a specific gear max acceleration occurs at maximum torque.

If the god like 'infinitely variable gearbox' was an option all you would care about is peak power.

Not quite. For any given vehicle speed, max acceleration occurs at peak torque. Maximum acceleration always will and only can occur, by definition, at maximum torque.

And if the infinitely variable gearbox were available then to reach the maximum rate of acceleration, you would only care about peak torque. To reach maximum speed, you would need to gear to maximum power

Quote:

Originally Posted by NISFAN

Nice write up ......but wrong Power is the real engine performance indicator

Physics would like a word with you

Remember that power is only the ability of a system to do work over time. Peak bhp is the point on the torque curve of a car where, for a given speed, the maximum amount of torque is available to the wheels. Sounds like it contradicts my earlier point but it's subtly different. Again, it's all to do with gearing. I could show you the equations but equations are really hard to do on a forum

Actually, I think I understand what you meant by "performance indicator". Inasmuch as a higher bhp figure is an indication that a car develops high torque at high rpm then yes, it is a good indicator of "performance".

But let's not forget that this is all in the context in which it was intended. The rate of acceleration is only ever governed by torque. Ever. The rate of acceleration is what makes a car feel quick to the driver, it is all we're aware of in terms of straight line performance as a driver. A car like the 30D will always feel quick in any gear whereas cars like the 335i and M3 will never "feel" as quick because they can never have the same amount of torque applied to the drivetrain. Thanks to gearing, they will be empirically quicker when driven in the higher rev ranges where they shine and as I've always said: they'd leave a 30D behind but again, nobody drives like that in the real world and they have to be driven like that to be as quick as a 30D - and will never feel as quick unless you're booting it at 7000rpm in third or something: an experience you can't match in a diesel.

So since these kind of cars require effort, revs and a lot of fuel to match the 30D's performance and even more to surpass it, in the real world of on-road driving, the 30D is the quicker car and torque is more important than horsepower.

You're kinda missing the point with this whole Torque Vs Power argument.

Soooo.... a couple of facts from the world of physics to help straighten things out Power (bhp/kW) is only a factor when it comes to ultimate, out-and-out top speed. That is all. End of. It has literally NO bearing on acceleration. None. Zip. Nada. Torque is the ability of the engine to turn the wheels and accelerate the car. Power is there to overcome overall friction - in this case in the form of tyre, air and mechanical friction.

Now you understand that, you'll understand why torque is all that matters in the real world. The reason that an M3 will accelerate faster than a 330D or any other high torque/low rpm car for that matter, is the way in which it delivers its power. The critical factor in this is the gearbox. A gearbox ... get this ... is a torque multiplier. That's all it is. Simples.

So take a 330D at 3000rpm giving out 400 ftlbs of torque (I'm making these numbers up for the sake of our little experiment here) and then take an M3 [i]at the same speed but in a different gear ratio so that it's at 6000 rpm and giving out 300ftlbs of torque. Since the M3 is at twice the engine speed of the 330D here, it is running twice the gear ratio and so its torque, relative to the 330D, is doubled. I'm not saying it's putting out 600ftlbs here, just that the final torque to the drivetrain will be double that of the 330D at the same speed in this instance. that's why an F1 car with a tiny 2.4l V8, putting out a miserly 200ftlbs of torque can move like the clappers. That 200ftlbs of torque is developed from 17k to 18k rpm so you get huge multiplication from the gearbox. Same goes for bikes.

However, and here's the killer, who drives like that on a normal day? Nobody for long anyway To get that "fast feeling" (which is simply forward acceleration for most people), one simply needs to put one's foot down in any gear at any speed in a car with tonnes of torque and you're off. A normal overtake from 60-80mph in top gear ... the 30D will hand the M3's ass back to it Most driving, done between 1500 and 4000 rpm is right in the 30D's sweet spot where maximum torque is available whereas the M3 isn't even on cam by then. Same goes for the 335i. And I know I've said this a million times (especially over in the American forum 'cause it's soooo rewarding) but the 335i and, to a lesser extent the M3, is only quicker than the 30D when you wind the nuts off it. Under all other circumstances, it's slower.

So next time you look at a car's performance figures, look a little closer and see the bigger picture. I honestly have no idea why the automotive world still goes on about bhp in 90% of cars. it only matters in hypercars where going over 200mph is an issue. What's your maximum torque and at what rpm is it developed. Only then can you compare like for like in the real world. And forget Top Gear lap times, they're only of use for entertainment (which they surely are) and are the TV equivalent of a bedroom poster. Torquey cars just feel quicker for 90% of driving. It's only a matter of physics and it's all about torque.

Simples

Thats a fair old write-up Maestro.
I'm a big lover of torque since I've started buying big diesel engine cars. Absolutely agree that day to day a big torque engine is much easier to drive quicker (and "feels" quick too).

But...... you want to put your post up on the E90post forum - watch the 335i guys start flaming .

Given the same gear ratios, yes. The 30D would "pull more G" than either a 335i or an M3. However, given gearing, the torque is multiplied at the wheels and so the actual peak acceleration of either is going to be higher when they're on full afterburner; especially the M3 because it's a high revving beast

I think this is where people (and by people, I mean 335i owning Americans) often misunderstand what I post when I bring up the subject. I have never debated whether or not a 35i is "faster" than a 30D, let alone an M3. All I have ever tried to point out, and now with a bit of layman-physics, is that under "normal" driving conditions, the 30D is actually, really and measurably faster than both.

If I can be bothered, I might even look up the gear ratios and see if I can find some torque curves for both the 30D and 35i and plug them into some equations in Excel to give an absolute rate of acceleration for any given speed in each gear. At least then we'd know precisely at what speeds and in what gears each is faster than the other

Who knows, I could end up looking a complete chump and find that the 30D is a slow, lumbering ox compared to the 35i but I suspect that isn't the case

One thing I've noticed with the E90 335d (yes diesel and not 335i !) is that due to its linear power delivery, it doesnt feel quite as urgent as the 330d, although its supposed to be a quicker car with more torque and power. Others have said this too.

Perception can be easily affected simply by the shape of the torque curve also. A very rapid change in the rate of acceleration (steep, almost vertical, front end to a torque curve) can be deceptive and make a car feel less quick than it really is. The 335i suffers from this in my opinion. It's near instantaneous torque and then completely flat for ages so there's no "surge"; no onset of boost; no feeling of the acceleration building whereas my MPS would build like a rampant rabbit from 2500 to 3500 rpm to a peak torque not that much higher than a 335i but it would always feel a tonne quicker. This is why I kept checking if I'd left the handbrake on or something crazy when I test-drove the 35i - it never fealt quick even though its figures are respectable.

I've never driven the 335D (hell, I haven't even driven my 30D yet!) so can't comment on them specifically but my modified MPS and a 335i are very close on paper but driving them back to back was chalk and cheese except my MPS couldn't deliver a 6-pot tingle as the rpms passed 5000